In the past of variety of different devices such as miniature knives, scissors and needles have been used to make surgical incisions in regions of limited volume such as in parts of the eye.
As an example, modern cataract removal techniques currently employ extra capsular cataract extraction. An essential step in this surgical procedure is the proper incision of the anterior lens capsule. This incision is usually carried out through a 3.0 mm to 4.0 mm limbal incision, to retain the closed condition of the eye. This small incision restricts the motion of the knife so that the leading edge of the cutting surface is rarely at right angles to the surface to be cut. To deal with this problem an "can opener" type of incision has been developed where multiple punctures are made into the anterior lens capsule. Then, the central portion of the anterior lens capsule is torn away from the peripheral portion. This results in a frayed edge with capsule strands which may complicate the remainder of the surgical procedure.
In addition, passage into and out of the anterior chamber represents a threat to the corneal integrity because of possible damage to Descement's membrane, as well as the corneal endothelium. There is also the possibility of a collapse of the anterior chamber each time an instrument, such as a sharp needle is withdrawn. Such a collapse can prove inimical to the iris, cornea and the lens.